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Community Member

CUCM8.0 - H323 gateway - codec negotiation issue


We have:

a CUCM8.0 cluster serving several sites.

2 C3945 routers configured as H323 gateway for 1 new site.

IP phones.

We configured 1 region for the new site, and G.711/G722 (64kpbs) is configured as the codec within the region. And in the voice gateways, dial-peers are configured to use G.711. But some calls from IP Phones terminating on the voice gateways are in G.729r8, and a lot of calls from IP phones heading to PSTN (via T1 trunks on the voice gateways) fail due to "resources unavailable" error.

All incoming calls are good, and when in SRST mode, all calls (outbound, inbound) are good.

We have tried IOS 15.0(1)M4 and 15.2(4)M3 but same result.

Anyone faced with this issue before? Any suggestions?




CUCM8.0 - H323 gateway - codec negotiation issue


let me get this straight: do you see that resource unavailable error for G.729 calls only or for both G.711 and G.729?


Community Member

CUCM8.0 - H323 gateway - codec negotiation issue

Successful PSTN calls could be either G711 or G729.

But for calls from IP phones and terminating on VoiceGW, G.729 calls would fail.

VIP Super Bronze

CUCM8.0 - H323 gateway - codec negotiation issue

You will need to check the region between the ip phones and the gateway. Most likely this is set to use G729..You can avoid all these issues by configuring a voice class codec on your gateway and assign that to your dial-peer rather than hardcoding a codec to it..


voice class codec 1

codec preference 1 g729r8

codec preference 2 g711ulaw

codec preference 3 g711alaw

dial-peer voice xx voip

voice-class codec 1

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